1. Field
The present invention concerns Bluetooth communications, and more particularly, a method and system for one Bluetooth device to conserve power during paging of other Bluetooth devices, and also to minimize the interference that such paging presents in the applicable frequency band. This is achieved by using transmit power that has been reduced in accordance with channel metrics measured during an earlier inquiry process.
2. Background
“Bluetooth” is a wireless personal area network technology supporting wireless voice and data communication between different nearby devices. A number of different devices can be Bluetooth-enabled, for example, cell phones, personal digital assistants, or laptop computers. Each such device is equipped with a receiver, transmitter, and other Bluetooth components, allowing it to communicate with other similarly equipped, nearby devices without the use of cables or other physical connections.
Operation of Bluetooth-enabled devices (“Bluetooth devices”) includes various operating processes and modes, as prescribed by the applicable Bluetooth specifications and standards. Briefly, in an “inquiry” process, a Bluetooth device sends a number of universally broadcast inquiry messages, called “inquiry IDs.” The inquiry process, performed to discover the presence of other “remote” Bluetooth devices within range, is an essential precursor to establishing a connection with one or more of these devices. As an example, a Bluetooth device may perform its inquiry process whenever a need (such as an operator request) arises to establish communications with a remote Bluetooth device.
After completing the inquiry process, a Bluetooth device proceeds to page one or more remote Bluetooth devices. For each device, paging is conducted for a prescribed time, such as 10.24 seconds. If the remote device answers the page during the prescribed time, the two devices cooperatively establish a connection during which data is exchanged, such as user, customer, subscriber, or other such data. Active mode communications involve the exchange of messages related to customer or subscriber data, in contrast with metadata and network data exchanged during idle or standby mode communications and not associated with customer/subscriber data.
In addition to the inquiry process, page process, and connection processes, Bluetooth devices perform a variety of other operating modes and processes as well. All communications are conducted in the unlicensed 2.4 GHz ISM (“Industrial, Scientific and Medical”) band, which spans a frequency range of 2400.0 to 2483.5 MHz in the United States and Europe. The ISM band is further divided into 80 RF channels or frequency bins, which are each 1.0 MHz wide.
In addition to Bluetooth devices, the ISM band is also occupied by systems that operate under the IEEE 802.11b specification for wireless local area networks (“IEEE 802.11b wireless systems”). Other devices such as microwave ovens also operate in the same ISM band. IEEE 802.11b wireless systems and microwave ovens operate in the ISM band at much greater transmit power than Bluetooth devices. Thus, due to the overlapping frequency bands and greater signal strength utilized by some non-Bluetooth devices, there is a possibility of such devices interfering with Bluetooth communications.
Signal interference, then, can be a problem during the Bluetooth inquiry process, during the page process, during established connections, and during all other operating modes. Conventional Bluetooth devices try to defeat signal interference in different ways during the different processes. In the page process, for example, known Bluetooth devices transmit their page signals at full transmit power regardless of the presence or absence of signal interference. The advantages of this approach are that it is uncomplicated and that it is likely to overcome any signal interference that might be present.
One unforeseen disadvantage of this approach, as discovered by the present inventors, is that when signal interference is low, the act of paging with full transmit power is unnecessary. Therefore, as further recognized by the present inventors, Bluetooth devices may utilize more power than necessary during page mode operations. And, since many Bluetooth devices operate on battery power, greater power consumption is undesirable because it drains the battery more quickly. Ultimately, the battery must be recharged, or if a recharging source is unavailable, the battery will cease to operate.
In addition to excessive power consumption, another disadvantage of conventional page mode operations, as recognized by the present inventors, is that use of full transmit power may increase the possibility of Bluetooth devices unnecessarily interfering with other Bluetooth and/or IEEE 802.11b wireless systems operating in the same area. For instance, paging with high transmit power may create signal interference for Bluetooth devices that are not being paged.
Although the construction and use of Bluetooth devices generally constitute significant advances, then, the present inventors have nonetheless discovered unforeseen problems with conventional Bluetooth devices.